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FLOTATION SEPARATION of SCHEELITE from FLUORITE and CALCITE X Qiu1, X Zhou1, H Hu1 and G Q Fu1

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FLOTATION SEPARATION of SCHEELITE from FLUORITE and CALCITE X Qiu1, X Zhou1, H Hu1 and G Q Fu1 Paper No. 145 FLOTATION SEPARATION OF SCHEELITE FROM FLUORITE AND CALCITE X Qiu1, X Zhou1, H Hu1 and G Q Fu1 ABSTRACT Ca-containing gangue minerals such as Fluorite, Calcite have same surface activity point--calcium ions and approximate floatability with scheelite, it is difficult to achieve good dressing index of rough concentrate of scheelite. Mono-mineral experiments and ore tests indicate that, according to mineral composition, gangue minerals can be inhibited selectively by adopting suitable regulators, then the separation of scheelite from gangue minerals can be realized effectively. Mechanism analysis was taken by zeta potentials measurements and FTIR tests. Good dressing indexes are also obtained in practical ore tests and industrial tests. Keywords: scheelite, fluorite, calcite, regulator, flotation separation INTRODUCTION In scheelite flotation, gangue minerals such as Fluorite and Calcite have the same surface-active cation (Ca2+ ) with scheelite minerals and strong binding capacity with the fatty acid collectors. So the floatability of scheelite is close with that of Fluorite and Calcite and it is difficult to get good scheelite rough concentrate indexes. It is necessary to research regulators with high selectivity to achieve good indexes for scheelite concentrate. THE FLOATABILITY TESTS AND DISCUSSION Preparation of samples and conditions The mono minerals were taken respectively from the rich ore of scheelite, Fluorite and Calcite by crushing, grinding and purification. The content of scheelite in the mono mineral is 91.45%, the content of fluorite is 99.90% and the content of calcite 99.90%. Finally, one part of the pure samples was treated to -0.074 mm by grinding and another part was treated to -0.002mm for zeta potentials measurements and FTIR tests. The reagent NaOH, which was used as a regulator in the flotation tests for mono minerals, was analytical reagent. The other reagents such as Na2SiO3, the new fatty acids collector TAB-3, common collectors sodium oleate and oxidized paraffin soap (733, 731) were all industrial products. As X Zhou (2010) showed that the new fatty acids collector TAB-3 have strong adsorption ability on scheelite and weak adsorption ability on the calcium minerals. All the flotation tests were done at the temperature of 30 in a 35ml flotation machine, and3.0 g sample is used in each test. After adding pH regulator, Na2SiO3 and collector sequently and the conditioning time is 2 min, 3 min and 4 min respectively. After flotation for 4 minutes, the℃ concentrate is achieved and weighted to calculate the recovery. The zeta potentials of minerals is measured by Zetaplus Zeta analyzer and every sample is measured three times and averaged. The infrared spectral analysis results are produced by FTIR tests. 1. Guangzhou Research Institute of Nonferrous Metals, Guangzhou, Guangdong PRC, 510650. Email: [email protected] XXVI INTERNATIONAL MINERAL PROCESSING CONGRESS (IMPC) 2012 PROCEEDINGS / NEW DELHI, INDIA / 24 - 28 SEPTEMBER 2012 04324 QIU et al The mono-mineral tests Effect of pH on the floatability of minerals The effect of pH on flotation performance of Scheelite, Fluorite and Calcite is shown in Figure 1 while the dosage of the reagent TAB-3 is 50mg/L and using NaOH as the regulator. Figure 1 shows that the floatability of Fluorite is better than that of Calcite. When pH > 6, the recovery of scheelite is higher than 90%. The floatability of scheelite is better when pH = 8.5 and is remarkably weakened when pH > 10. Figure 1. Effect of pH on flotation performance of Scheelite, Fluorite, and Calcite Effect of TAB-3 dosage on the floatability of minerals The effect of TAB-3 dosage on flotation performance of Scheelite, Fluorite and Calcite was studied at the condition of pH 8.5 and only the reagent TAB-3 is added. The results are shown in Figure 2. From Figure 2, the recovery of Scheelite increases visibly with the increase of the TAB-3 dosage. XXVI INTERNATIONAL MINERAL PROCESSING CONGRESS (IMPC) 2012 PROCEEDINGS / NEW DELHI, INDIA / 24 - 28 SEPTEMBER 2012 04325 FLOTATION SEPARATION OF SCHEELITE FROM FLUORITE AND CALCITE Figure 2. Effect of TAB-3 dosage on flotation performance of minerals when pH is 8.5 Effect of pH on the floatability of minerals when using Na2SiO3 The effect of pH on flotation performance of Scheelite, Fluorite and Calcite is shown in Figure 3 while the dosage of the reagent Na2SiO3 is 400 mg/L and using NaOH as the regulator. From Figure 3, the recovery of Fluorite and Calcite reduces obviously when 8.0<pH<11.0. When pH≥11.0, the recovery of Fluorite reduces sharply with the increase of pH, but the recovery of calcite increases obviously. Figure 3. Effect of pH on flotation performance of scheelite, fluorite and calcite when using Na2SiO3 XXVI INTERNATIONAL MINERAL PROCESSING CONGRESS (IMPC) 2012 PROCEEDINGS / NEW DELHI, INDIA / 24 - 28 SEPTEMBER 2012 04326 QIU et al Effect of Na2SiO3 dosage on the floatability of minerals While the dosage of the reagent TAB-3 is 100 mg/L, pH=10 and using NaOH or Na2CO3 as the regulator, the effect of pH on flotation performance of Scheelite, Fluorite and Calcite is shown in Figure 4. Figure 4. Effect of TAB-3 dosage on flotation performance of minerals when using Na2CO3 or NaOH as pulp regulators respectively From Figure 4, the floatability of Scheelite, Fluorite and Calcite is better when using Na2CO3 as the regulator. However, when using NaOH as the regulator, the Na2SiO3 can depress Fluorite obviously when the dosage is above 400 mg/L. The surface potential results of minerals and discuss Effect of pH on the surface potential of minerals While using NaOH as the regulator and undergoing a reaction with the reagents, the relation between pH and the surface potential of Scheelite, Fluorite and Calcite is shown in Figure 5. Figure 5. The relation between pH and the surface potential of scheelite, fluorite and calcite （CNa2SiO3＝400mg/L，CTAB-3＝100mg/L；1.scheelite；2.fluorite；3.calcite） XXVI INTERNATIONAL MINERAL PROCESSING CONGRESS (IMPC) 2012 PROCEEDINGS / NEW DELHI, INDIA / 24 - 28 SEPTEMBER 2012 04327 FLOTATION SEPARATION OF SCHEELITE FROM FLUORITE AND CALCITE From Figure 5, when using the reagent TAB-3 and Na2SiO3, the surface potential of scheelite shifts slightly and the surface potential is closely with that, only when the reagent TAB-3 is used, the surface potential of fluorite shifts a bit further and is different from that of only using the reagent TAB-3; the surface potential of calcite shifts the farthest. Effect of Na2SiO3 dosage on the surface potential of minerals While the dosage of the reagent TAB-3 is 100 mg/L, pH=10 and using NaOH or Na2CO3 as the regulator, the relation between the dosage of Na2SiO3 and the surface potential is shown in Figure 6. Figure 6. Effect of Na2SiO3 dosage on the surface potential of minerals when using Na2CO3 or NaOH as pulp regulators respectively （CNa2SiO3＝400mg/L，CTAB-3＝100mg/L；1.scheelite；2.fluorite；3.calcite） From Figure 6, the surface potential of Scheelite, Fluorite and Calcite in Na2CO3 is higher than that in NaOH. The order of the surface potential difference extent between the two solution mediums is scheelite<fluorite<calcite. The IR results of the reagent TAB-3 and minerals IR of the reagent TAB-3 Figure 7 shows the infrared spectrum of the reagent TAB-3. In the infrared spectrum, the peak at 2921.6 cm-1 -1 wave number was assigned to C-H asymmetric stretching vibration in -CH3 bond and the peak at 2854.1 cm wave number was assigned to C-H symmetric stretching vibration in -CH2 - bond. The peak of C-O stretching vibration in carboxyl group is around 1560.1cm-1. 100 80 60 Transmittance 1560.1 40 2856.1 2921.6 4000 3500 3000 2500 2000 1500 1000 500 -1 wavenumber(cm ) Figure 7. Infrared spectrum of the reagent TAB-3 XXVI INTERNATIONAL MINERAL PROCESSING CONGRESS (IMPC) 2012 PROCEEDINGS / NEW DELHI, INDIA / 24 - 28 SEPTEMBER 2012 04328 QIU et al IR of minerals after using the reagents Figure 8 shows the infrared spectrum of Scheelite, Fluorite and Calcite treated with Na2SiO3 and TAB-3. 6 2865.7 5 2921.6 2861.8 4 2854.1 2921.6 3 Transmittance 1560.1 2854.1 2921.6 2 1546.6 2921.6 2854.1 1 1560.1 2854.1 2921.6 4000 3500 3000 2500 2000 1500 1000 500 Wavenumbers(cm-1) Figure 8. Infrared spectrum of scheelite, fluorite and calcite after treatment with sodium silicate and TAB-3 1.Scheelite + TAB-3; 2.Scheelite + sodium silicate + TAB-3; 3.Fluorite + TAB-3; 4.Fluorite + sodium silicate + TAB-3; 5.Calcite + TAB-3; 6.Calcite + sodium silicate + TAB-3 From Figure 8, it shows as follows: Firstly, the peak of C-O stretching vibration in carboxyl group around 1546.6cm-1 is found in Scheelite, and as Guoxi Zheng (1983) showed, the peak around 1546.6cm-1 is the dominant peak in calcium acid. Secondly, the peaks of C-H asymmetric stretching vibration in -CH3 bond around 2921.6cm-1 and C-H symmetric stretching vibration in -CH2- bond around 2854.1cm-1 are found in Fluorite, but no peak of associating O-H stretching vibration is found. Thirdly, the peak of C-H asymmetric stretching vibration in -CH3 bond around 2921.6cm-1 is not found in calcite. DISCUSSION AND ANALYSIS OF THE RESULTS Through the solution chemistry of Na2SiO3 in flotation, analysis on the Zeta-potential and infrared spectrometry of the mineral surface and the reagent TAB-3, the influence mechanism of regulators on the floatability of Scheelite, Fluorite and Calcite is studied and discovered.
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